Lock stitch post sewing machine



Dec. 4, 1962 R, REEBER ErAL Loox sIIIcH PosI SEWING MACHINE Filed May 4, 1962 ...ln-I

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United States Patent Office I `3,066,625 Patented Dec. 4, 1962 3,066,625 LCK SlfilCH PGS? SEWING MACHWE Rudolf Recherand Reinhold Dobner, Kaisersiautern,

Pfalz, Germany, and Svend Astrupgaard, Lynghy,

Denmark, assigner-s to G, M. Pfaff AG., Kaisersiautern,

Pfalz, Germany Filed May 4, i962, Ser. No. @2,442 Claims priority, application Germany .lune 6, 1961 3 Clair-ns. (Ci. lf2-214) The invention relates to sewing machines and is particularly concerned with a lock stitch sewing machine of the type in which the bottom feeding means are mounted in raised position on a standard or post.

Known sewing machines of this type rely for feeding the material either on a feed wheel or on a feed dog of the type which executes a rectangular movement. ln both cases the machines are constructed in a manner that the lock stitch catch which moves horizontally is disposed on one side of the needle as viewed in the direction of forward feed, while the feeding means is provided on the other side of the needle.

The post sewing machines provided with a bottom feed wheel provide the advantage of feeding the material in a rather favorable manner but they have the shortcoming that particularly due to the necessary lateral arrangement of the driving means for the feed wheel a cross section of considerable magnitude is required for the post. Furthermore, there is only a relatively small surface area available for placing the material for conventional sewing operations because it is only that part of the post surface which is on the side of the feed wheel which serves for placing the material. Such machines thus have the shortcoming that the post area available on the side of the catcher cannot be used for supporting the material being sewn and in addition, the sewing of closed shoe shafts, for example of childrens shoes, is considerably encumbered in that it is not possible to hang the shaft over the post owing tothe large cross sectional area of the post.

For these reasons therefore, in actual praxis primarily such work is performed on post sewing machines which are equipped with a hopper transport. As a result of this the small width of the feed dog and of its driving means a somewhat smaller post is obtained, but on the other hand, such machines have the disadvantage when working with leather that uneven stitch lengths occur as a result of the elliptic path of the feed dog and thus a seam of unattractive appearance is formed. Furthermore, owing to the periodic jerky movements and the repeated setting at rest of the material ybeing sewn, the guiding and the observing of the material is encumbered. For example, in the production of fancy seams the material has to be kept under careful observation which results in rapid fatigue of the eyes of the seamstress.

A further disadvantage inherent in the known post sewing machines is that as a consequence of the arrangement of the looper and feeding means on different sides of the needle, it is difficult to provide cutting means. This has resulted in mounting the cutting device in machines with minimum cutting distance on the arm of the machine. The relatively long lever arm of the cutter which is necessary for such construction causes oscillation phenomena which have a disadvantageous effect on the cutting operation.

A machine is known having a feed wheel which is inclined perpendicularly with respect to the direction of feed and which is driven by a conical toothed gear which meshes with the feeding teeth. The horizontally disposed catcher drive shaft which is arranged parallel to the drive shaft of the toothed gear at a distance that is equal to the sum of the two radii of the feed wheel and the toothed gear carries the catcher or looper at its forward end where it rotates inside the plane of rotation of the feed wheel. The ring shaped feed wheel is guided in circumferential grooves of the cylindrical material carrier while the upper half of the material carrier is recessed to accommodate the looper. This machine, however, is one which has a rotating lock stitch looper, the diameter of which, as is well known, is considerably smaller than that of the feed wheel, so that here no difficulties arise in accommodating the looper within the feed wheel.

It is an object of the invention to provide a possibility in lock stitch sewing machines to manage with a post type material support of minimum cross section which, while eliminating the aforementioned shortcomings, insures of secure support of the material to facilitate stepping down of shafts, particularly of closed shafts of small sizes. In accordance with the invention this is facilitated in that the lock stitch looper and the feed wheel which are annularly shaped are arranged on the same side of the needle in such spacial environment that the looper point projects through the hollow inner space of the feed wheel.

By arranging the looper and the feed wheel on one side of the needle, a post cross section of optimum smallness is obtained because the post is only negligibly wider than the diameter of the lock stitch looper. The entire post surface may thus be utilized for supporting the material, while the side of the needle opposite the post is freed for cutting devices. This provides the possibility of mounting cutting devices at a minimum cutting distance on the post.

Furthermore, it is made possible for the first time in accordance with the invention to provide double needle post sewing machines with a 'bottom feed wheel or bottom feed wheels and thus on the one hand facilitate the operation of these machines and on the other hand to essentially increase the productivity or eihciency of such machines.

The looper operates especially well if the upper half of the circular surface defined by the feed wheel can remain `free of control parts for the feed wheel. in accordance with `a further object of the invention this is achieved in that the ring shaped feed wheel which has a conical inner surface is rotatably journalled only along portions of its inner circumference upon a conical support formed in the manner of segments and arranged below the center of the feed wheel. The segment type support provides effective guidance for the feed wheel while the looper point for taking up the loop projects uninipededly through the hollow inner space of the feed wheel so that the thread can neither wedge or become hooked in or on the feed wheel or on any guide parts thereof.

A particularly advantageous construction of the post as lfar as small cross `section is concerned is obtained in 0 that the drive shaft for the feed wheel is arranged coaXially with respect to the looper drive shaft. This provides the possibility of forming the post also in the direction of feed only negligibly wider than the diameter of the looper. Closed shafts of small and smallest sizes may thus extend beyond the post.

Further objects and advantages will become apparent from the following specification and with reference to the drawings which illustrate an embodiment of the invention and in which:

FIG. l is a full front View of a sewing machine incorporating the invention;

FIG. 2 is a front view of the post partly in section; and

FG. 3 is a section taken along the line III-Ill in FIG. 2.

The sewing machine comprising a base plate 1, post 2, socket 3, arm 4 and head 5 is illustrated in FIG. l. A

o support arm 6 is secured to the head 5 o-f the machine which rotatably carries an upper feed wheel 7. The arm 4 accommodates in the usual manner the arm shaft `8 which at its forward end has driving engagement with the needle bar 9 which is reciprocably movable in the head 5. t

The arm shaft drives likewise in a known manner a toothed wheel 11 mounted, on hollow shaft 16` by way of a reduction gear (not shown). The hollow shaft 10 which is journalled in two bearings 12, 13 is provided at its lower end above the toothed wheel 11 with a set collar 14 `for securing the axial position while a friction wheel 15 is provided at the upper end. The friction wheel which is provided with `a friction surface 16 has an annular surface -17 which runs on a surface 118 defined on the post 2 thus securing the hollow shaft in axial direction.

The feed teeth 19 of an annular feed wheel 20 provided to the left of the needle are in meshing engagement with the friction Wheel 15. The feed wheel 20 is provided with a conical inner surface 2.1 and is guided by a segment type support 23 having a conical counter surface 22. The support mounted below the center of the feed wheel by means of screws 24 on wall 26 of the post 2 with cup springs 25 therebetween affords slight axial movement of the feed wheel thereby avoiding wedging of said wheel.

The horizontal drive shaft 27 for the lock stitch looper 31 journalled in the base plate 1 is also driven by the arm shaft 8 in a known manner (not illustrated). The shaft 27v is provided with a pinion gear 28, the counter gear `29 `of which is secured on the -looper drive shaft 30 :arranged coaxially with the hollow shaft 10.

The vertical looper shaft 30 journalled in the hollow shaft .10 supports the lock stitch looper 31 at its upper end. The looper is arranged in such a manner that its point 32 projects through the upper half of the circular hollow space defined by the feed wheel 20 while the looper point for picking up the loop extends the required distance to the needle center for catching the loop.

To stop the vertical looper shaft axially a collar ring 33 of eccentric conformation is secured on the shaft below the looper and is operated by a known airing device 34 for the housing. The collar ring is supported on a sleeve 36 provided on an arm 35 and arranged around the hollow shaft.

The side wall 38 of the post is secured by means of a screw 37 to the arm 35 of the sleeve 36 and has a hinge 39 around which a cover plate 4G is pivotally movable which plate constitutes the supporting surface for the material. In this manner the looper is readily accessible from the upper surface of the post.

Having now described our invention with reference to the embodiment illustrated, we do not wish to be limited thereto, but what we desire to protect by Letters Patent of the United States of America is set forth in the appended claims.

We claim:

1. Post step stitch sewing machine of the type having a ybase, a machine arm extending over said base and supporting a drive shaft, a machine head disposed endwise of said arm, a needle bar mounted in said machine head, operatively connected to said drive shaft and extending downwardly therefrom and supporting a needle at the lower end thereof, a post extending upwardly from said base toward said needle and needle bar, said post having `a material supporting surface :at the upper end thereof, an annular feed wheel disposed in generally vertical position in the upper end of said post and having a portion of its periphery proximate said surface, and a looper mounted generally horizontally in said post substantially -at a right 4angle to said feed wheel, said feed wheel and said looper beind disposed Ialong the same side of the operating path of said needle, and said looper .having a catcher point extending through said feed wheel.

2. Post step stitch sewing machine of the type having a base, a machine arm extending over said base and supporting a drive shaft, a machine head disposed endwise of said arm, a needle bar mounted in said machine head, operatively connected to said drive shaft and extending downwardly therefrom and suporting a needle at the lower end thereof, a post extending upwardly from said base toward said needle and needle bar, said post having a material supporting surface at the upper end thereof, an annular feed wheel disposed in generally vertical position in the upper end of said post and having a portion of its periphery proximate said surface, and a looper mounted generally horizontally in said post substantially at a right angle to said feed wheel, said feed wheel and said looper being disposed along the same side of the operating path of said needle, and said looper havJ ing a catcher point extending through said feed wheel, said feed wheel having an inner surface of conical configuration, a support for said feed wheel in the form of a` segment having conical opposite surfaces in engagement with portions of said inner surface of said feed wheel, said feed wheel being rotatable on said support.

3. Post step stitch sewing machine of the type having a base, a machine arm extending over said base and supporting a drive shaft, a machine head disposed endwise of said arm, a needle bar mounted irl said machine head, operatively connected to said drive shaft and extending downwardly therefrom and supporting a needle at the lower end thereof, a post extending upwardly from said base toward said needle and needle bar, said post having a material supporting surface at the upper end thereof, an annular feed wheel disposed in generally vertical position in the upper end of said post and having a portion of its periphery proximate said surface, and a looper mounted generally horizontally in said post substantially at a right angle to said feed wheel, said feed wheel and said looper being disposed along the same side of the operating path of said needle, and said looper having a catcher point extending through said feed wheel, said feed wheel having an inner surface of conical configuration, a support for said feed wheel in the form of a segment having conical opposite surfaces in engagement with portions of said inner surface of said feed wheel, said feed wheel being rotatable on said support, and a horizontally disposed friction wheel for driving said feed wheel disposed substantially at right angles to said feed wheel in driving engagement therewith, a vertically disposed hoilow shaft for supporting and driving said friction wheel and a vertically disposed looper shaft for supporting and driving said looper mounted concentrically with said hollow shaft.

References Cited in the file of this patent UNITED STATES PATENTS 2,250,616 Zonis July 29, 1941 2,669,206 Pinkvoss et al Feb. 16, l954 2,863,410 Lange et al Dec. 9, 1958 2,875,716 Pinkvoss Mar. 3, l959 

